<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        p {
            display: flex;
            width: 500px;
            height: 200px;
            background-color: pink;
        }
        span {
            width: 100px;
            height: 100px;   
        }
        p span:nth-child(1) {
            width: 50px;
            background-color: blue;
        
        }
        p span:nth-child(2) {
            background-color: yellow;
            flex: 1;
        }
        p span:nth-child(3) {
            background-color: purple;
            width: 50px;
        }
    </style>
</head>
<body>
    <p>
        <span></span>
        <span></span>
        <span></span>
    </p>
</body>
</html>